I always argue that 1) Glock's OE magazine tube and 2) the OE Magazine Catch are two critically important components to ensure the "out-of-the-box" reliability that Glock is famous for. That is because 1) the factory magazine lips dictate the feed angle of the cartridges relative to the feeding ramp and 2) the factory cut notch for the mag catch and the OEM mag catch dictate exactly where and at what angle the loaded factory magazine is positioned inside the grip frame....
For these reasons and because of its length, I too am NOT interested in SA Z9 magazine for the G43 at all. I would rather keep using my "proven to me" MagGuts'ed OEM magazines in my G43s, even though they offer a couple of rounds less than the Z9 mag....
That being said, and fully understanding the "increased risk of undermined reliability" when "grip-chopping" the G43X and using entirely aftermarket magazines and an aftermarket steel magazine catch,
the size of the "grip-chopped G43X" combined with a "flush-fit 10-rounder magazine" is still too attractive for me to just dismiss/ignore (IF the combination works reliably with JHP ammo)...

That is basically my dream "G43 update," which Glock as the original manufacturer should be making with the OEM flush-fit 8-rounder mags...
As I said in the beginning, this is a solution to a non-existent problem. Want a small gun, carry the 43, want more rounds, carry the 43X and/or extra magazines.
Actually this is definitely one "possible" solution to
a real existing problem with the original G43, which Glock still refuses to update...
We G43 fanboys are greedy, so we want a small Glock pistol of the G43 size but also want a few more rounds without extending the grip length.

(Yeah, I've already got a P365, but it ain't a Glock, ya know?

) However, because this "possible" solution comes with the "reasonable risk" of undermined reliability," many of us the G43 fanboys are still hesitant to try it....